Separating plate assembly for treatment of suspension

ABSTRACT

A multi-stage separating plate assembly comprises a plurality of vertical rows of inclined separating plates arranged in a zig-zag series of plates, said rows being laterally spaced to form a liquid guide path between adjacent rows. A given separating plate at any stage in one of said rows has the lower end thereof extending across the major part of the guide path which it partially defines and close to the upper surface of the next lower separating plate in the adjacent row inclined in the opposite direction.

United States Patent [1 1 3,727,770 Mochizuki 1 Apr. 17, 1973 [54]SEPARATING PLATE ASSENIBLY FOR 531,798 l/l922 France ..2lO/52l TREATMENTOF SUSPENSION Tadao Mochizuki, 648-735, Hatsutomi, Kamagaya City, ChibaPrefecture, Japan Filed: June 7, 1971 Appl. No.: 150,530

Inventor:

Foreign Application Priority Data July 31, 1970 Japan ..45/67097 US. Cl..2l0/522 Int. Cl. ..B0ld 21/24 Field of Search ..2lO/52l, 522, 532

References Cited FOREIGN PATENTS OR APPLICATIONS 333,730 12/1903 France..2lO/52l Primary Examiner-Reuben Friedman Assistant Examiner--F. F.Calvetti Attorney-Wenderoth, Lind & Ponack ABSTRACT 11 Claims, 17Drawing Figures lllllllllll IIIIIIIIIIVIIIIIIIIIIII PATENTEU 719753,727, 770

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INVENTOR BY MMGZJJM ATTORNEY PATENTEDAPR 1 H973 SHEET 3 [1F 3 FIG.

TADAO MOCHIZUKI,

INVENTOR ATTORNEYS SEPARATING PLATE ASSEMBLY FOR TREATMENT OF SUSPENSIONBACKGROUND OF THE INVENTION clarified liquid which is substantially freeof the settled particles, through the use of a plurality of verticalrows of a zig-zag series of separating plate members, said rows beinglaterally spaced to form a liquid guide path between adjacent rows.

The hitherto known apparatus of the aforementioned type employs aplurality of vertical rows of inclined separating plates so arrangedvertically that the adjacent separating plates in the same row areinclined in substantially opposite directions to each other in such amanner as to allowing the lowermost end of the upper plate to projectslightly downwardly over the uppermost end of the lower plate. When thesuspension is introduced into a settling tank with such a separatingapparatus, the suspended particles are progressively thrown from thesuspension against the upper surface of each inclined separating plateand then the settled particles successively slide down on the said uppersurface toward the upper surface of the next lower separating plate at alower stage in the adjacent row while passing across the liquid guidepath formed between the adjacent rows. A clarified liquid zonesubstantially free of the settled and suspended particles, which zone isestablished in each liquid guide path, is therefore disturbed by thedescending flow of the settled particles, resulting in a poor separationefficiency. Furthermore, when treating a suspension liable to flow in adense current, such a suspension tends to flow toward the bottom of thetank because the guide path is of a vertically continuous chimney-likeform. This causes the upper portion of the apparatus not to act as aseparating apparatus, resulting in only partial settling and a poorseparation efficiency.

SUMMARY OF THE INVENTION In accordance with the invention, a multi-stageseparating plate assembly is provided comprising a plurality oflaterally spaced zigzag vertical rows each having inclined separatingplates successively arranged above one another and inclined alternatelyin substantially opposite directions each separating plate at any stagein one of said rows having a partition wall extending downwardlytherefrom close to the upper surface of the next lower separating platein the adjacent row and across the major part of the space between theadjacent rows. In a settling tank equipped with such an improvedseparating plate assembly, the settled particles thrown from thesuspension onto the upper surface of each separating plate at any stagein one of said rows can slide down toward the upper surface of the nextlower separating plate in the adjacent row without disturbing a claifiedliquid zone substantially free of the suspended and settled particles,and since the liquid guide path is partitioned by the partition wallsprovided on the separating plates, the suspension has no tendency toflow toward the bottom of the tank.

An object of the present invention is therefore to provide an improvedseparating plate assembly of the type described which promotesefficiency in subjecting the suspension to segregation.

Other objects and advantages of the present invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which similar reference charactersdenote similar parts throughout the figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic cross sectionof one example of a settling tank in which a separating plate assemblyof the present invention is contained;

FIGS. 2 to 11 are diagrammatic fragmental views of different embodimentsof the present invention, each showing a cross section of a portion ofthe separating plate assembly;

FIG. 12 is a view for explanating one feature of the present invention;

FIGS. 13 and 14 are diagrammatic views for explaining a process forclarification of the suspension in the separating apparatus of FIGS. 2to 6 and FIGS. 7 to 1 1, respectively;

FIGS. 15a and 15b each show diagrammatically a portion of a conventionalseparating plate assembly, in section; and

FIG. 16 is a diagrammatic view for explaining a disadvantage of theconventional assemblies of FIGS. 15a and 15b.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings andin particular to FIG. 1, there is shown a multi-stage separating plateassembly of the present invention installed in a settling tank A in aconventional manner, which tank is shown here as having a substantiallyrectangular cross-sectional shape by way of example. However, the tankmay be of any cross sectional shape desired. A suspension that is to besubjected to separation in the tank A is fed horizontally i.e., in adirection perpendicular to the surface of the drawing at a suigablespeed. As will be appreciated, the tank A may be or may not be of abatch type.

For a better understanding of the present invention, certainconventional separating apparatus of the type described will be firstillustrated in detail in conjunction with FIGS. 15a and 15b prior to thedescription of the preferred embodiments of this invention.

FIG. 15a shows a part of a conventional multi-stage separating plateassembly which comprises a plurality of laterally (i.e., in a directionperpendicular to that of suspension flow) equispaced vertical rows 6a,6b, and 6c, each consisting of a plurality of separating plates 1', 2and 3' alternately inclined in substantially opposite direction relativeto each other and arranged in a zigzag series. Therefore, any pair ofadjacent zigzag rows of plates define between them a liquid guide path5'. In operation, for each guide path 5', there are created a zone x ofa clarified liquid a along the lower surface of each of the inclinedseparating plates 1, 2 and 3, a zone y of settled materials, i.e.,concentrated particles b settled on the upper surface of each of theseparating plates, and an intermediate zone 2 existing between thesezones 1: and y. In the zone z, the separation of the clarified liquid afrom the suspended particles b is in progress. The collections of theparticles b settled on the upper surface of each of the separatingplates 1', 2' and 3' are caused by the gravity acting thereon tosuccessively descend or slide down across the intermediate zone 2, withthe attendant disadvantage that the liquid in the intermediate zone 1 isremixed with the descending particles b. Additionally, such descendingparticles b once separated from the liquid medium are also remixed withthe ascending clarified liquid a in the zone x every time it goesthrough successive gaps 4 provided between the adjacent plates of eachrow. That is, a portion of the settled particles b in the vicinity ofeach gap 4 is attracted as shown by solid arrows toward and entangledinto the ascending flow of the clarified liquid a shown by dottedarrows.

With the aforesaid conventional separation apparatus, as describedabove, the unfavorable remixing of the concentrated particles b with theclarified liquid a and the liquid in the intermediate zone 1 occursthroughout the whole separating plate assembly, resulting in a poorseparation efficiency of the apparatus.

FIG. b shows another embodiment of a conventional separating apparatus,in which each gap 4' is reduced in width in order to eliminate theabovementioned disadvantage. In such an apparatus with the reduced gaps,however, a portion of the clarified liquid a ascending along the lowersurface of each separating plate tends to move upwardly away from adirection of inclination of the associated separating plate and acrossthe guide path 5, so that the settled particles b sliding down along theupper surface of the associated separating plate, e.g., the separatingplate 1' in the row 6b are scattered about, whereupon a portion of thesettled particles b are remixed into the flow of the clarified liquid aalong the lower'surface of the separating plate 1 in the adjacent row6a. This also results in a poor separation efficiency of the apparatus.

Another problem lies in the fact that in these prior art apparatus eachguide path 5 is chimney-like in form extending between the adjacent rowsof the multistage separating plates continuously from the surface of theliquid to be treated to the bottom of the tank with approximately samewidth. This fact causes, where it is necessary to continuously treat aliquid Q liable to flow in a dense current, such as a liquid of highdensity or a liquid containing heavy particles in suspension, a downwardflow of the liquid of the abovementioned kind to build up in the tank Aas shown in FIG. 16. Accordingly, the upper portion of the apparatus isutilized hardly at all and does not act as a separation apparatus. Inother words, only some separating plates effectively act on the liquidto be treated and the liquid flows out over an overflow weir 9 withoutcomplete settling of the suspended particles. In FIG. 16, referencenumeral 8 represents an evener wall with a plurality of holes for thesuspension to pass through.

A further problem lies in the fact that as the guide path 5 continues toextend vertically in the abovementioned manner, there can occur, in eachguide path 5', counter flows extending in upward and downward directionsdue to the counter flows of the settled particles b and clarified liquida, i.e., the ascending flow of the clarified liquid 0 along the lowersurface of each separating plates and the descending flow of the settledparticles b along the upper surface of each separating plate. This alsoresults in a poor separation efficiency.

This invention provides a multi-stage particleseparating plate assemblyhaving an improved efficiency of separation of the suspended particlesfrom the suspension thereof.

Referring now to FIG. 2, there is shown a part of an embodiment of amulti-stage particle separating plate assembly according to theinvention which assembly is somewhat similar to those of FIGS. 15a and15b except that there is no gap between adjacent particle separatingplates of the same row and each liquid guide path between adjacent rowsis partitioned by partition walls extending from the lower ends of theassociated particle separating plates across the liquid guide path. Itis to be understood that, although the three-stage particle separatingplate assembly comprising three rows each consisting of three particleseparating plates is shown, the assembly may employ any desired numberof rows each consisting of any desired number of particle separatingplates.

In FIG. 2, reference numerals 1, 2 and 3 show particle separating plates(which may be referred to as first, second third-stage particleseparating plates, respectively) inclined alternately in oppositedirections to each other and successively arranged to form a zigzag rowof particle separating plates. In this manner, a plurality of rows 6a,6b and 6c are provided in a laterally equispaced relationship.Preferably, all of the particle separating plates in the same stage areinclined in the approximately same direction and all of the particleseparating plates in the next stage are inclined in the substantiallyopposite direction to that of the first stage of particle separatingplates. Each of the particle separating plates. 1, 2 and 3 are providedat its lower end with a partition member 10 which downwardly extendsacross the major part of the liquid guide path 5 between the adjacentrows and close to the upper surface of the lower next stage particleseparating plate in the adjacent row and ending just short of the nextlower stage plate to leave a space 13 between the lowermost end of themember 10 and the said upper surface. The partition wall 10, therefore,partitions the associated liquid guide path 5 and intermediate zone Zinto parts.

The partition wall 10 is illustrated as being an integral part of theassociated particle separating plate, however, it need not be anintegral part.

It is noted that the space 13 has to be large enough to allow thesettled particles b to pass easily therethrough and to present them frompassing across the intermediate zone z.

In operation, when the settling tank A is supplied with a suspension,the suspended particles b in the suspension begin to settle under theaction of gravity onto the upper surface of each of the separatingplates 1, 2 and 3 and then slide down through each spaces 13 toward theupper surface of each of the lower stage separating plates in theadjacent row. That is to say, the suspended particles b settled on theupper surfaces of the first and second stage separating plates 1 and 2in the row 6b slide down respectively onto the upper surfaces of thesecond stage separating plate 2 in the lefthand row 6a and third stageseparating plate 3 in the righthand row 60 without passing across theintermediate zone z, in which the settling of the suspended particles bis in progress, and then successively through the spaces 13 toward thebottom of the tank A. Although the settling operation has been describedin conjunction with the specific separating plates, it is to beunderstood that such a settling movement occurs throughout the particleseparating assembly. In the meantime, the clarified liquid a obtainedascends in the clarified liquid zone x along the lower surface of eachof the separating plates 1, 2 and 3 and collects in a trigonal space 14defined by the partition member and the upper portion of the separatingplate in the next lower stage to the separating plate from which thepartition member extends. With respect to the separating plate assemblyof FIG. 2, the movements of the clarified liquid a and suspendedparticles b are shown'in FIG. 13. Namely, the particles bl, b2 and 173in the respective stages settle slowly during the travel of thesuspension from the inlet to the outlet of the apparatus, and in themeantime the clarified liquid is produced in each stage as shown by thehatched portion of the figure and flows substantially horizontallytoward the weir 9.

As described hereinbefore, the present invention has provided animproved apparatus in which each separating plate has a partition wallso depending therefrom as to interrupt the intermediate zone between anypair of adjacent zigzag rows of the separating plates. With such anapparatus, the settled particles sliding down the plates are preventedfrom passing across the intermediate zone in the guide path, and areallowed only to move down onto the upper surface of the next lower stageseparating plates in the adjacent row. It is stated again that thisresults in overcoming the following disadeantages of the heretoforeknown apparatus;

1. Both the intermediate zone in which the segregative treatment of thesuspension is being effected to a certain extent and the ascendingclarified liquid separated from the suspended particles are agitated dueto collision with the already settled out particles; and

2. The settled out particles are taken up into a continuous flow ofclarified liquid passing upwardly through the gaps along the lowersurface of each of the separating plates.

Furthermore, the apparatus of the present invention provides a guidepath which is partitioned by the partition walls so that it is not avertically continuous chimney-like space tending to cause counter flowsin the guide path and therefore the liquid in such an apparatus is notagitated. In addition, the apparatus according to the invention can beadapted for the treatment of a liquid which would create a current,resulting in extreme improvement in separation efficiency.

With respect to the embodiments shown in FIGS. 3 to 6, at substantiallymidway of the height between the lower and upper ends of each pair ofsuccessive separating plates 1 and 2, and 2 and 3 in each row, there isprovided a pair of vertically extending opposed portions 12, having abar 11 fixed thereto to carry the separating plate assembly. Thesupporting bar 11 may be connected to the portions 12, either bydirectly joining them together or by means of fittings.

In FIG. 3, for example, one of the paired portions 12, is provided atthe lower end of the partition wall 10 of the separating plate 1 in therow 6b and the other is provided at a corresponding portion of theseparating plate 2 in the adjacent row 6a. The paired portions 12, arespaced a suitable distance to form the said space 13 therebetween.

In FIG. 4, for example, one of the paired portions 12, is provided atthe base of the partition wall 10 of the separating plate 1 in the row6b and the other is provided at the upper end of the separating plate 2in the same row.

The assembly of FIG. 5 is similar to that of FIG. 4 except that eachpartition wall 10 extends vertically downwardly rather then obliquely.

The assembly of FIG. 6 is similar to that of FIG. 3 except that theupper portion of the separating plate above the portion 12 extendsvertically upwardly rather then obliquely.

These embodiments shown in FIGS. 3 to 6 have the same separating effectat that described in conjunction with FIG. 2. It is to be noted that,with the apparatus shown in FIGS. 2, 3 and 4, since the settlingdistance h in the guide path is substantially uniform as shown in FIG.12, i.e., there is no portion having an extremely large settlingdistance, there is no possibility that the suspended particles b willoverflow with the horizontal flow without settling and the time requiredfor the treatment of the suspension is not prolonged.

FIG. 7 shows still another embodiment of the assembly, the constructionof which is similar to that of FIG. 2 except that a gap 4 is formedbetween the successive separating plates in the same row. In operation,when the suspension to be treated enters the tank, the suspendedparticles b in the suspension descend in the direction of the gravityand are deposited on the upper surface of each of the separating plates1, 2 and 3. Then, the settled particles on the upper surfaces of, forexample, the separating plates 1 and 2 in the row 6b slide downrespectively onto the upper surfaces of the separating plates 2 and 3 inthe adjacent rows 6a and 60 without passing across the intermediate zone1 in the associated guide path 5. In this manner, the settled particlesb successively slide down stepwise toward the bottom of the tank. At themeantime, the clarified liquid is created below the lower surfaces of,for example, the separating plates 2 and 3 and continuously flows in azigzag path in the vertical and horizontal component directions throughthe gaps 4 along the lower surfaces of the separating plates while beingseparated from the particles b sliding-down and reaches the uppersurface portion of the liquid to be treated, from which it is directedtoward the overflow weir 9 (FIG. 14). The movements of the suspendedparticles b and clarified liquid a are shown in FIG. 14, from which itwill be appreciated that the settling of the suspended particles bl, b2and b3 in the respective stages is completed during their travel fromone end to the other of the apparatus and in the meantime more clarifiedliquid a is produced in the higher portion of the tank than in the lowerportion as shown by the hatched portion because of the presence of thegaps 4. Therefore, a larger volume of the clarified liquid can flow outof the tank, resulting in a high separating efficiency.

According to the arrangement of FIG. 14, an improved separation efiectcan be expected because the clarified liquid ascends while flowing inthe horizontal component direction. The clarified liquid in thearrangement of FIG. 2 goes only with the horizontal flow toward theoverflow weir 9. Furthermore, even when treating a liquid havingsuspended particles and a liquid medium between which a relatively greatdifference in specific gravity exists, there is no possibility ofcausing the inconvenience of the clarified liquid produced in eachcompartment defined by, for example, the partition wall of the plate 1of the row 6b, the mid portion of the plate 2 of the row 6a, thepartition wall 10 of the plate 2 of the row 6a and the upper portions ofthe plates 2 and 3 of the row 6b, running over this compartment andconsequently ascending toward another upper compartment over theextremity of the partition wall 10 or through the spacing 13 to cause adisturbance in the liquid.

It will therefore be understood that in the arrangement of FIG. 7, likethe embodiment shown in FIG. 2, there is no disturbance in the liquiddue to the slidingdown movement of the settled particles in the vicinityof the gap 4 opening into the guide path, no remixing of these settledparticles into the ascending clarified liquid, and no influence ofcurrent due to the density of the liquid.

Further embodiments are shown in FIGS. 8 to 11 which correspond inconstruction to the embodiments shown in FIGS. 3 to 6, respectively,except that the gap 4 is formed between successive separating plates ofthe same row. Therefore, these embodiments have the same effect as theembodiments of FIGS. 3 to 6.

Although various specific embodiments have been described above, it willbe readily understood by those skilled in the art that variousrearrrangements of parts and modifications of parts may be accomplishedwithout departing from the spirit and scope of the invention.

What I claim is:

l. A multi-stage separating plate assembly for subjecting asubstantially horizontally flowing suspension to a separation intosettled particles and clarified liquid, comprising a plurality oflaterally equispaced vertical rows each consisting ofa plurality ofseparation plates extending substantially parallel to the flow of thesuspension and alternately inclined in opposite directions and arrangedin a zigzag series, the corresponding separating plates on the samehorizontal level being inclined in the same direction and forming astage of plates and two adjacent rows forming a suspension guide paththerebetween, each of said separating plates in each row having at itslower end a partition member extending across the guide path andterminating close to the upper surface of the separating plate which isin the now adjacent thereto and which is one stage below said separatingplate, thereby to partition the major part of said suspension guide pathformed by said two adjacent rows and thereby to form a trigonal space ineach row defined by said partition member and the upper portion of theseparating plate in the same row and one stage below said eachseparating plate, whereby the clarified liquid collects in said trigonalspace and flow of settled out particles from the portion of the guidepath above the partition can flow to the portion of the guide path belowthe partition without interfering with the clarified liquid or beingdisturbed by the flow of the clarified liquid in said trigonal space.

2. An assembly according to claim 1 wherein each partition memberextends in the same direction as the inclination of said separatingplate.

3. An assembly according to claim 1 wherein the free end of each of saidpartition members and a corresponding portion of said separating platespaced from said free end are bent substantially vertically and a barattached to the vertically bent portions in each stage to carry themulti-stage separating plate assembly.

4. An assembly according to claim 3 wherein the upper portion of each ofsaid separating plates above said bend thereof extends verticallyupwardly until it reaches the separating plate one stageabove said eachseparating plate.

5. As assembly according to claim 1 wherein, in each row, the lower endof one of said separating plates and the upper end of the separatingplate in the stage below said one separating plate are bentsubstantially vertically and a bar attached to the bent portions in eachstage to carry the multi-stage separating plate as sembly.

6. An assembly according to claim 5 wherein said partition membersextend vertically downwardly.

7. An assembly according to claim 1 wherein, in each row adjacentseparating plates are spaced to leave therebetween a gap for clarifiedliquid produced in each trigonal space to pass upwards therethrough.

8. An assembly according to claim 7 wherein the free end of each of saidpartition members and a corresponding portion of said separating platespaced from said free end are bent substantially vertically and a barattached to the vertically bent portions in each stage to carry themulti-stage separating plate assembly.

9. An assembly according to claim 8 wherein the upper portion of each ofsaid separating plates above said bend thereof extends verticallyupwardly and stops just short of the separating plate one stage abovesaid each separating plate to leave said gap between said upper portionand the lower surface of the separating plate one stage above said eachseparating plate.

10. An assembly according to claim 7 wherein, in each row, the lower endof one of said separating plates and the upper end of the separatingplate in the stage below said one separating plate are bentsubstantially vertically and a bar attached to the bent portions in eachstage to carry the multi-stage separating plate assembly.

11. An assembly according to claim I0 wherein said partition membersextend vertically downwardly.

1. A multi-stage separating plate assembly for subjecting asubstantially horizontally flowing suspension to a separation intosettled particles and clarified liquid, comprising a plurality oflaterally equispaced vertical rows each consisting of a plurality ofseparation plates extending substantially parallel to the flow of thesuspension and alternately inclined in opposite directions and arrangedin a zigzag series, the corresponding separating plates on the samehorizontal level being inclined in the same direction and forming astage of plates and two adjacent rows forming a suspension guide paththerebetween, each of said separating plates In each row having at itslower end a partition member extending across the guide path andterminating close to the upper surface of the separating plate which isin the row adjacent thereto and which is one stage below said separatingplate, thereby to partition the major part of said suspension guide pathformed by said two adjacent rows and thereby to form a trigonal space ineach row defined by said partition member and the upper portion of theseparating plate in the same row and one stage below said eachseparating plate, whereby the clarified liquid collects in said trigonalspace and flow of settled out particles from the portion of the guidepath above the partition can flow to the portion of the guide path belowthe partition without interfering with the clarified liquid or beingdisturbed by the flow of the clarified liquid in said trigonal space. 2.An assembly according to claim 1 wherein each partition member extendsin the same direction as the inclination of said separating plate.
 3. Anassembly according to claim 1 wherein the free end of each of saidpartition members and a corresponding portion of said separating platespaced from said free end are bent substantially vertically and a barattached to the vertically bent portions in each stage to carry themulti-stage separating plate assembly.
 4. An assembly according to claim3 wherein the upper portion of each of said separating plates above saidbend thereof extends vertically upwardly until it reaches the separatingplate one stage above said each separating plate.
 5. An assemblyaccording to claim 1 wherein, in each row, the lower end of one of saidseparating plates and the upper end of the separating plate in the stagebelow said one separating plate are bent substantially vertically and abar attached to the bent portions in each stage to carry the multi-stageseparating plate assembly.
 6. An assembly according to claim 5 whereinsaid partition members extend vertically downwardly.
 7. An assemblyaccording to claim 1 wherein, in each row adjacent separating plates arespaced to leave therebetween a gap for clarified liquid produced in eachtrigonal space to pass upwards therethrough.
 8. An assembly according toclaim 7 wherein the free end of each of said partition members and acorresponding portion of said separating plate spaced from said free endare bent substantially vertically and a bar attached to the verticallybent portions in each stage to carry the multi-stage separating plateassembly.
 9. An assembly according to claim 8 wherein the upper portionof each of said separating plates above said bend thereof extendsvertically upwardly and stops just short of the separating plate onestage above said each separating plate to leave said gap between saidupper portion and the lower surface of the separating plate one stageabove said each separating plate.
 10. An assembly according to claim 7wherein, in each row, the lower end of one of said separating plates andthe upper end of the separating plate in the stage below said oneseparating plate are bent substantially vertically and a bar attached tothe bent portions in each stage to carry the multi-stage separatingplate assembly.
 11. An assembly according to claim 10 wherein saidpartition members extend vertically downwardly.